I delivered in the private section of QMH. Basically one main difference with public is that you work with one obgyn during the full pregnancy. It's not guaranteed that he/she will be at the delivery, but in my case my doctor was. Another difference is that you stay in a private or semi-private room, in a separate (more quiet) section. Visiting hours were a bit flexible as well. And I noticed that the food I got was different, more choice I believe? That's about it. You deliver in the same delivery rooms, you go to the same informative talks.
I think my costs for room/ vaginal delivery were a little over 50K (2yrs ago) and doctor charges were approx HKD1000 each time.
Bear in mind that costs could exceed this if there are complications. That's why I this time (yes pregnant again!) am going public now that my insurance has changed and covers less... I think the only thing I would miss is the private room, so I could spend quiet time with hubby and baby.